1. Field of the Invention
The present invention relates to a semiconductor package and method of fabricating the same, and more particularly, to a semiconductor package having enhanced heat dissipation and method of fabricating the same.
This application claims priority to Korean Patent Application No. 2005-0000805, filed on Jan. 5, 2005, the subject matter of which is hereby incorporated by reference in its entirety.
2. Description of the Related Art
Although semiconductor device size has decreased over time, the number of input/output pins on a semiconductor device has risen dramatically, as has semiconductor device operational speed. Accordingly, semiconductor devices consume more electric power per unit volume, and generate more heat than they did previously. The heat generated greatly increases semiconductor chip temperature, which slows down semiconductor chip operating speed.
The heat generated by a semiconductor chip in a semiconductor package is dissipated to the exterior of the package mostly through a substrate, such as a printed circuit board (PCB), while the rest of the heat is absorbed by the area surrounding the semiconductor chip. However, the dramatic decrease in package size has limited the amount of heat that may effectively be dissipated through the substrate, so a large amount of heat remains in the area surrounding the semiconductor chip. Therefore, a heat spreader has been introduced into the semiconductor package to help the semiconductor chip dissipate heat.
FIG. 1 is a cross sectional view of a semiconductor package comprising a conventional heat spreader.
Referring to FIG. 1, the semiconductor package comprises a substrate 10, such as a printed circuit board (PCB). A circuit pattern is formed on one side of a substrate 10, and both sides of substrate 10 may be coated with a passivation layer 14, such as a photo solder resist layer. A semiconductor chip 22 comprising a plurality of bonding pads (not shown) is adhered to a top surface of substrate 10 by a non-metallic adhesive 20 such as an epoxy resin. Substrate 10 and semiconductor chip 22 are electrically coupled by a wire bonding 24. A ball terminal 16 is adhered to a ball terminal land 18 formed on a bottom surface of substrate 10. Reference symbol 12 denotes a generic illustration of a redistribution pattern. Redistribution pattern 12 electrically connects the plurality of bonding pads to ball terminal lands 18.
A heat spreader 28 is molded on semiconductor chip 22 with a molding material 26 that covers side surfaces and an upper surface of semiconductor chip 22. Heat spreader 28 may be completely covered by molding material 26, or it may be partially covered, exposing an upper surface of heat spreader 28, as shown in FIG. 1. Heat spreader 28 is formed from a material having relatively high heat conductivity such as aluminum or copper, and a surface of heat spreader 28 is black filmed by CuO or Cu2O to enhance heat dissipation.
A semiconductor package comprising a conventional heat spreader 28 has several problems. First, heat spreader 28 increases the weight of the package, and the weight increase may decrease the durability of the package, which may be weakened by physical shock. That is, the circuit pattern of the package may be easily cracked by the physical shock resulting from being dropped, for example. However, the weight of heat spreader 28 may not be one of the factors considered when maximizing the heat dissipation of a semiconductor package. Secondly, since conventional heat spreader 28 is adhered to substrate 10 with epoxy resin, conventional heat spreader 28 may cause a heat gradient between layers or elements within the package. The heat gradient may lead to cracking of layers or elements, such as a via, within the package during a heat reliability test conducted after increasing the heat stress of substrate 10. Thirdly, heat is indirectly dissipated through molding material 26, which has a relatively low heat conductivity, because heat spreader 28 is not connected directly to wire bonding 24.